1. Field of the Invention
The present invention relates generally to a position lock for locking the positions of a plurality of cylindrical elements, and more particularly pertains to a needle position lock having a provision for selectively locking and unlocking the positions of one or more needles in place to avoid inadvertent movements and positioning errors thereof.
The following discussion is specific to one embodiment of a needle position lock. Attaining and maintaining accurate needle positioning is one of the most time consuming and tedious steps in the Brachytherapy seeding procedure for placing radioactive seeds in a patient to treat prostrate cancer. Once a needle has been positioned to the correct depth, it is important that its position be accurately maintained during subsequent steps of the procedure. The needle may have an applicator or seed cartridge attached to it prior to the release of seeds. The needle may also be positioned as one of a row of needles positioned at one time. The force required to move a needle out of position is relatively low, and a needle might be accidentally moved out of position without the person releasing the seeds noticing it. In addition, the needle hubs are small and located in close proximity to one another when they are positioned in a group. This also makes it easy to inadvertently move one or more needles without detecting the positioning error. Existing needle guide templates have no provision for selectively locking and unlocking the position of each needle in place to avoid such positioning errors.
2. Discussion of the Prior Art
Current practice in the art uses a needle guide template having an ordered array of holes to guide the needles during insertion. The needle guide template uses adequately close-fitting holes, combined with an engagement depth of ten diameters or more, to effectively control angular misalignments and assure that the needles have axial (depth) movement only. However, the equipment has no provision to prevent inadvertent needle movement between initial insertion of the needle and the delivery of the radioactive seeds.
Accordingly, it is a primary object of the present invention to provide a position lock having a provision for selectively locking and unlocking the positions of one or more substantially cylindrically shaped elements such as needles in place to avoid inadvertent movements and positioning errors thereof.
Although the disclosed embodiment is for a needle position lock, the position lock is applicable to locking the position of any substantially cylindrical shaped elements such as probes and electrodes.
A more specific object of the subject invention is the provision of a needle position lock comprising a disposable template assembly having front and back templates halves which define an array of close-fitting through-holes to guide needles therethrough. The front and back template halves are held in radial alignment with each other by mating bosses to assure smooth and accurate guiding of the needles during insertion. In usage, the two halves are fastened firmly together, and preferably include snaps to allow the disposable template assembly to be inserted into a reusable or disposable mounting bracket for usage during a surgical procedure, and then detached and discarded. A series of lock slides locks the positions of columns of needles positioned within the template. Each lock slide locks the position of one or more needles inserted into one or more series of holes in the template, with a preferred embodiment locking needles in two series of holes. For a typical template arrangement, six lock slides are used to lock twelve series of needles inserted into holes in the template assembly. Additional series can be added or subtracted in increments of two or one. If desired a single column could be operated by a single lock lever.
The present invention prevents inadvertent needle movement between initial insertion of the needle and delivery of the radioactive seeds therethrough. This invention is described in terms of a needle position lock to assist a Brachytherapy seeding procedure, but could easily be adapted to lock and unlock needle positions for other minimally invasive procedures using any types of needles, or adapted to lock and unlock the positions of any substantially cylindrically shaped elements such as probes or electrodes.
The present invention comprises a needle position lock with a needle guide template which defines a hollow center between front and back halves thereof to accept needle lock slides. Each needle lock slide has the capability of locking one or more series of needles, in one or more series of holes in the template by an axial locking or unlocking movement applied by a locking lever or cam. When the lock slide is moved axially, a locking wedge/clamp collar engages with and locks each inserted needle. The needle is axially locked in position by a combination of a wedging action, due to the tapered, wedge-like profile of the hole in the wedge/clamp collar, and by a clamping action provided by flexure of the wedge/clamp collar and its attachments to supporting compression elements. Once clamped, each needle is locked to the lock slide, which is retained positioned inside the front and back template halves. This prevents the needle from moving axially until the locking lever is released and the lock slide is moved to an unlocked position. This configuration allows a column or row of needles to be easily and quickly locked in position after insertion, and then unlocked once any attachments have been. made, and the surgeon is ready to retract the needles and deliver the seeds.
In one embodiment of a typical template arrangement, a number n of lock slides could be used to lock a number of 2n holes in the template. In some embodiments a single lock slide could operate a single column of holes. Alternatively, a second series of wedge/clamp collars might be positioned inside a blank portion of the template. The second series of wedge/clamp collars might also be eliminated from the last lock slide in some embodiments.
A typical lock slide includes a main body with three compression elements attached to a beam, a beam cam surface for engagement with a cam lock lever, and a slotted cam follower pin to facilitate retraction and unlocking thereof. In a typical embodiment, two series of thirteen wedge/clamp collars each could be positioned between the compression elements, with each wedge/clamp collar being attached to each adjacent compression element by a semi-flexible member on each side thereof Each wedge/clamp collar preferably resembles a horse collar with a gap at one side. The portion of the hole inside the wedge/clamp collar and adjacent to the gap preferably provides a slip fit for the needles. The portion of the hole spaced from the gap is preferably rounded, but slightly smaller in diameter than the needle diameter. The sides of the hole between the larger and smaller portions preferably resemble a wedge with rounded ends. The semi-flexible members are preferably configured to transmit axial motions with a force required to translate the collar and wedge around the needle. Also, the semi-flexible members could flex slightly, causing the wedge/clamp collar to pinch closed, clamping down around the needle.
A cam lock lever with both external and internal cam surface provides the motion and force required to actuate the lock slide. The lock lever is rotationally mounted to the template halves, with the lever moving back and forth to move the lock slide and lock or unlock the needles. The cam locking lever has both outer and inner cam surfaces. The outer cam surface engages the beam of the lock slide, pushing it to lock. The inner cam surface engages a lock slide follower pin to pull it when the position of the lock lever is reversed. The cam surfaces and material friction properties are preferably optimized to cause the lock lever and lock slide to stay unaided in either the locked or unlocked position.
The present invention allows a surgeon to insert a needle to the desired position in the prostrate, then easily lock it in position with the simple flip of a lever. This allows the needle and seeds to remain in position after they are initially accurately positioned.
A surgeon can easily insert and position up to a whole column or row of needles in sequence, locking each one in turn. A current common practice is for an urologist to insert and position one needle at a time, and then wait for an oncologist to deliver the seeds before inserting another needle. Being able to confidently insert, position, and lock up to a whole column or row of needles in sequence, the urologist would then be free to insert a column or row of needles in another patient in an adjoining surgical suite while waiting for the oncologist to deliver the seeds. Alternatively, the oncologist could deliver seeds to another patient while waiting for the urologist. The present invention frees and enables both the urologist and oncologist to operate more independently for larger periods of time, thereby increasing productivity.
The total procedure time is reduced, since less time is lost while the urologist and oncologist trade places. In addition, less time is lost due to needles being accidentally bumped out of position, thereby causing the urologist to go back and position the needle for a second time.
Finally, instances of a needle being accidentally bumped out of position and the mislocation going undetected should be reduced, resulting in the seeds being delivered more closely to the treatment plan with more consistent results.